Electroplating method and apparatus



H. C. LUECHAUER ELECTROPLATING METHOD AND APPARATUS July 12, 1960 :sShets-Sheet 1 Filed Sept. 5, 1957 k ivk svs INVENTOR.

B -/0//e C. Luechaue/ His Alto/nay I July 12, 1960 H. c. LUECHAUERELECTROPLATING METHOD AND APPARATUS 3 Sheets-Sheet 3 Filed Sept. 5, 1957B olle 0. Luec/muer His Afro/nay 2,944,947 QPL T G ME QD ND A PARA WHqlle C. Luechauer, Dayton, Ohio, assignor to General MotorsCorporation, Detroit, Mich., a corporation of De aware Filed ept. 5,1951,-Se r. No. 682,127 11 .Claims. (Cl. 204-26) invention relates toelectroplating and is particularly'concerned with an apparatus andmethod. for

the invention to utilize a plating tank having "a trackpassingtherethrough which divides the tankinto substantially two compartmentswherein the bearings to'be' plated are conveyedon the track'which islongitudinally apertured forlacting as a shield to'provide plating 'ofthe bearing surfaces.

The electrolyte which leaks out of the tank around the track ingress andegress is continuously replaced whereby the electrolyte level'in theplatingtank ismaintained substantially constant' iIn carrying" out theabove object, it is a further object of the invention to plate theconcavesurfa'c'esof senticylind-rical bearings wherein the'bearings'do'not necessarily require electrical connections in the'pla'tingcircuit whereby the movement of the bearings in the continuous platingprocess is facilitated.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to theaccompanyingdrawings wherein preferred embodiments of the invention are clearlyshown.

In the drawings:

Figure 1 is a sectional view taken through a plating tank including, atrack conveyor'therethrough havinga plurality ofbearings thereon.

Figure 2' is a fragmentary view of feeding apparatus shownimFigure-l inanother position.

Figure 3' is a fragmentary view showing the feeding apparatus ofFigure 1instill another position.

Figure?! is a sectional view ofanother type of'plati'n'g tank utilizingacontinuous belt conveyor 'ther'ein;

Figure 5 is al sectionalFvie'w taken on line 55 of Fig.1..

:Eigure 6-is a. sectional-z view taken on line 6 -6 of Figure 4;

.Figure 7 is a' fragmentary top view of'a portion of the track showninFigu'resf4 an'cl 6. V i Figure 8 is a fragmentary view of the topportion of the tank showing another "mean's'fors upplyingf current forelectroplating the Semicylindrical' bear' gs p'resent a rather diflicultprpb 1611i ftwd fi i F anna of bea n' s r s he??? These bearingsfareconvenj "nany p lated' on the. bearing surfaces withla very thintrolledfelectroplate in-the oirder of frOmQO'QOS to A 1 inchthick,which:plate must 15s uniform :and coe xten ve: is gene ally a;coplate invo atea-me q d nr lea s; of this general nature 1 are, fully WU FP ti -sur e e- B arin B atented July 2, 1966 2 is bonded to a steelbacking and wherein the surface of the aluminum is plated with ababbitt.

The plating operations in the past have been carried out in a batchprocess wherein the bearings are placed boxes, for example, as shown inPatent 2,761,831. These boxes are apertured at the front thereof wherebythe bearing surface is partially shielded for providing a uniformthickness of electroplate over the bearing surf c her f,

.In this disclosure, the bearings have a brush contact at the back sidethereof which is connected to the negative pole of a current sourcewhile the anode is connected to the positive pole of'said source, saidanode may be formed from the. metals to be plated or from certain of themetals with the others being added to the electrolyte as is well known.Suitable plating solutions arewell known in the :art and Patent 2,586,100 sets forth specifically two such solutions for plating lead-tinand lead tin-copper onto the surface of a bearing such as an aluminumbearing.

In copending application, S.N. 665,503, filed June 13,

11957, and assigned to the assignee of the present invention, anothertype of plating method is set forth wherein bearings areplated in abox-like structure having shielding means for providing uniform platingon the semiylindrical concave surfaces thereof and wherein a cathodeplate is used so that the bearing per se is not directly connected inthe circuit, This cathode plate substantially eliminates back plating ofthe hearing which is highly desirable and likewise eliminates thenecessity of direct electrical connections to the bearings.

The present invention is specifically directed to ap par'a'tiis and aplating method which is continuous in its operation so that any numberofbearings may be fed to and removed from the apparatusprogressivelywhen they are properly plated and wherein the apparatus operatesthroughout the day and thus eliminates the necessity of loadingtheplating boxes and placing them in plating tanks, etc, as se't forth inthe prior art as explained herein. This enables the user to elfecttremendous savings] in the operation.

Referring specifically to Figure 1, one form of the invention is shownwherein a plating tank 20 is provided havingentrance and exit apertures22 and 24 in the endwalls26 'and 28 thereof respectively. The specificshapje'of the apertures is shown in Figure 5. The plating tank 20 ismaintained Within a second tank 30 which is disclosed atent2,i8,6,()99;wherein an aluminum layer 7 larger and which acts as a meansfor collecting electrolyte which leaks out of the tank 20 as will bedescribed hereinafter. Passing through the tank 20 and fixedly fastenedtherein is a track 32 which, like the tanks 20 and 30; is formed fromnonconducting material or is rubber plated as is well known in the artso that it is not attacked or affected by the electrolyte. The track32*as shown in Figure 5 divides the tank 20 into two longitudinallyextending compartments, namely, an upper compartment 34 and a lowercompartment 36. The track is longitudinally apertured at 38 preferablywith a continuous slot or a plurality of interrupted slots as shownhereinafter so that, when a bearing 4t) is set thereon in invertedposition, the concave surface thereof faces the aperture 38. Theaperture 38 is dimensioned so as to provide a shield 'for the bearingtoeffect a uniform plating on the surface thereof as is Well known in theart. The track 32'has longitudinally extending ridges 42 and 44 thereonwhich fixedly position the bearings 40 transversely of thetrack-but'which permitthe bearings to be moved longitudinally thereof. 1

in practice, assho'wn inFi'gure 1, aplurality of bearings 4d aresuppliedto the track from a feed device 50 which includes" a verticle magazine52 having a cam operatedstop 54therein which stop is synchronized 3 vwith a cam operated pushing device 56. The timing of thepushing device56 is calculated in accordance with the length of the plating tank sothat bearings passing through the tank are immersed in the electrolyte asufli- "cient length of time to accumulate the desired amount ofelectroplate at their concave surfaces. Each time the pushing device 56moves to a position as shown in Figure 2, one bearing begins to pass outof the tank and another bearing begins to pass in. At the end of thestroke as shown in Figure 3, the release stop 54 is retracted to permitanother bearing to fall into position on top' of the pushing devicewhich, as it is retracted to the position shown in Figure 1, permits thebearing to fall onto the track while the stop 54 is again effective inthe magazine. Thus, the feed device 50 progressively feeds bearings tothe track, passes them through the tank and ejects them from the tank atthe opposite end thereof when the concave surfaces thereof are plated.

In the lower compartment 36 of the tank, there are positioned aplurality of transversely disposed rods 60 which span the tank and actas a bed for anode plates 61 which are plates of the metal to be platedsuch as lead-tin alloy, for example. These plates are slipped into thetank and onto the bed racks as they are needed and carry current fromone to another through contact. In the upper compartment 34, there ispositioned .a longitudinaly. extending metallic plate 62 which extendsthroughout the length of the compartment directly above the bearings.This plate acts as the cathode as set forth in the aforementionedcopending. application S.N. 665,503. The plate 62 may be steel, copper,etc., as determined by the'electrolyte used. Since the track 32 dividesthe tank into tow compartments wherein there is no free flow within theelectrolyte from one compartment to the other, there is little or noback plating of the bearings and substantially all of the electroplatedeposits on the concave surfaces thereof.

At the entrance and exit 22 and 24 respectively of the track, two plugmembers 66 and 68 respectively are placed which are attached to the tankwall and pass up wardly through the slot 38 and which more or lessconform to the concave surfaces of the bearings. It is understood thatthese plug members are of insuflicient size to bind on the bearings butare sufiicient to reduce the free flow of electrolyte outwardly of thetank. However, it is apparent that considerable electrolyte does flowout of these openings 22 and 24 which electrolyte is caught in the outertank 30. Pump means 70 in the outer tank 30 operate to replenishelectrolyte in the plating tank 20. The pump means 70 are adjusted so asto maintain the levelof electrolyte in the tank 20 constant regardlessof the amount of leakage around the track. In this manner, bearings areprogressively supplied and removed from the track and pass through theplating tank and are plated at the concave surfaces thereof. Anode metalis added when needed and electrolyte is also replenished for strengthand quantity when needed as is well known in the art. The cathode plate62 does not accumulate much plate thereon since there is little or nofree flow past the track. Whenever the cathode plate does accumulatesufficient plate thereon to warrant removal, it is replaced and strippedand subsequently reused. 1

It is understood that other types of feeding devices may be used andthatdeviations in design may be made without departing from the spirit of myinvention, for example, the plugs 66 and 68 are not necessary if thepump means. 70 hassufiicient capacity to maintain the level ofelectrolyte in tank20 above the cathode 62. Similarly, ifit is desiredto have direct electrical contact to the bearings instead of using acathode plate 62 out of physical contact with the bearings, it can beaccomplished as shown in Figure 8 by providing a cathode formed from aplurality of chains '63 or rollers, etc., attached to a cathode plate65, which drag over the upper surfaces of the bearings to provide a lowfriction contact as the bearings are moved through the electrolyte whichchains are connected to the negative source of current and supplycurrent directly to the bearings. In this instance, there will be moreback plating but since the electroplating being deposited is criticaland very thin, the back plating is generally not too objectionable incertain instances although, generally, the use of apparatus as shown inFigure 1 is more desirable.

Figure 4 shows another type of apparatus similar to the apparatus shownin Figure 1. In this embodiment, a plating tank is used which has acontinuous elastomeric track 102 passing therethrough that is carried bya pair of plastic, or rubber-covered rollers 104 and 106. Supportingrollers 108 are positioned where needed to maintain the tracksubstantially level. The track 102 is apertured in the form of a slot oras an interrupted slot such as a pluralityof aligned diamonds, '(seeFigure 7), circular holes, etc., as shown in Patent 2,761,831, whichapertures are spacedso as to be aligned with the bearings 40 as they arefed to the track through a cam operated feeding device 110 whichfunctions in a somewhat similar mauner to the device 50 previouslydescribed. In this instance, however, a double escapement is used whichis operated by cams 111 and 113 that are synchronized with the movementof the track 102 so that bearings fall onto the track in timed relationto longitudinal movement of the track. The track is rotated by means ofa suitable drive 112 connected to a motor 114. In this instance, plugs116 and 118 are supplied for the openings at the ends of the tank whichplugs are held on elongated supports 120 and 122, respectively, attachedto the outer tank 30. All other phases of the operation arethe same asthat described in connection with Figure 1 including the pump 70, thecathode 62 and anodes 61. Similarly, the cathode 62 may be replaced bycontacts as previously described. 7

It is apparent that the present invention provides a means wherebycontinuous plating operations may be carriedout on a plurality ofsemicylindrical bearings by merely feeding the bearingsto the platingtank whereby the bearings pass through the tank in a predeterminedperiod of time and are ejected therefrom in plated condition. It ismanifest that this operation greatly reduces the cost and complexity ofthe plating operations heretofore used on semicylindrical bearingswherein a batch process was used that required many manual operationssuch as loading of the boxes, positioning the boxes and removal of theboxes from the plating tank.

It is also to be understood that the bearings entering the feedingdevice 50 or 110 may be supplied thereto continuously from a cleaningvat or other previous operation. Similarly, as the bearings leave theplating operation, they may either fall into a bin or may be transferredto another conveyor whereupon they pass through washing operations,etc., as is well known in the art. In fact, all steps in conventionalelectroplating operations, other than the actual electroplating step,have heretofore been feasible in continuous operation but, until theprescathode and their connections, must be electrically nonconductive.These parts may'be made from plastic or rubber-like material or theymaybe made from metal coextensively covered with plastic or rubber, orsimilar nonconductive material as is well known in the art.

While the embodiments ofthe present invention as herein disclosedconstitute preferred forms, it is -to be 4* a 1:3 is-c a mesi as folows:

1.1.. Inv aumethod for co tin o s y e p a in the Q IQ W JIfi QQS. o aplurality of semicylindrical'bearings, the s eps compr sin providi a pll n taining anelectrolyte, providing a longitudinally apertured conveyortrack within said tank for longitudinally i id ng h t nk nta We gm ameats dina e a i d ic e r n s 9 sa 1; 9 .11% e bearin bu n n thertmdbrilswtr aperture lhQh' L99 cave surfaces facing the aperture and act as abarrier toward free passage of electrolyte from one compartment toanother through said aperture, positioning an anode in the lowercompartment of said tank beneath said track and insubstantially parallelrelation thereto, positioning a conductive plate in the uppercompartment above said bearings and in substantially parallel relationto said anode, electrically connecting the anode and the plate toopposite poles of a current source, progressively moving the bearingsalong said track and between the anode and the plate while maintainingthe aperture bridged by said bearings, and maintaining the electrolyteat a level suificient to cover said plate at all times.

2. In a method for continuously electroplating the concave surfaces of aplurality of semicylindrical bearings, the steps comprising; providing aplating tank containing an electrolyte, dividing said tank into twolongitudinally extending superimposed compartments by providing alongitudinally apertured conveyor track within said tank, feedingsemicylindrical bearings to said track so that the bearings abut oneanother and bridge the aperture with their concave surfaces facing theaperture and act as a barrier toward free passage of electrolyte fromone compartment to the other compartment through said aperture,positioning an anode in the lower compartment of said tank beneath saidtrack and in substantially parallel relation thereto, positioning aconductive plate in the upper compartment abovesaid bearings and insubstantially parallel relation to said anode, electrically connectingthe anode and the plate to opposite poles of a current source,progressively moving the bearings along said track while maintaining theaperture bridged by said bearings, and pumping sufficient electrolyteinto said tank to maintain the electrolyte level substantially constantand sufficient to cover said plate at all times.

3. In a method for continuously electroplating semicylindrical bearingsat the concave surfaces thereof wherein a tank is provided for theelectrolyte which includes a divider track therethrough. for dividingthe tank into two superimposed compartments, said track including alongitudinal aperture therein and having a cathode and an anode disposedin opposed relation on opposite sides of the track with the cathodebeing positioned above the track, the steps comprising; progressivelyfeeding semicylindrical bearings to the track in abutting relation sothat the concave surfaces of the bearings face the aperture and bridgethe aperture and prevent free passage of electrolyte from onecompartment to the other, electrically connecting the cathode and anodeto opposite poles of a current source, continuously plating the concavesurfaces of bearings with the tank progressively moving bearings alongsaid track and out of said tank, and continuously supplying sufficientelectrolyte to the tank to maintain the level of electrolyte thereinabove the said cathode.

4. In a method for continuously electroplating semicylindrical bearingsat the concave surfaces thereof wherein a tank is provided for theelectrolyte which includes a divider track therethrough for dividing thetank into two superimposed compartments, said track including alongitudinal aperture therein and having an anode disposed beneath thetrack, the steps comprising; progressively feeding invertedsemicylindrical bearings to the track in abutting relation so that theconcave surfaces of the bearings bridge the aperture and face theaperture and prevent free passage of electrolyte from one compartment tothe other establishing, an electrical circuit including the bearings.and the anode forelectrodepositing anode metal on the concavesu'rfacesofthe bearings, re plenishing electrolyte in the tank for maintaining alevel thereof sufiicient to immerse completely the bearings during theplatin re igd and a re ve re o bearings from the track at the endopposite to the end at which the bearings are fed to the track.

5a lh tmeflt d shined. in shim 4 wherein th l n ea htu gt stem a arlished .by pump e ectro y into the tank from a reservoir surroundingthe tank and having a level of electrolyte therein considerably belowthe normal level of electrolyte in the tank.

6. Apparatus for continuously electroplating semicylindrical bearings,comprising in combination; a first tank adapted to hold electrolyte andincluding apertures at opposite ends thereof, a longitudinally extendingapertured track connecting said apertures at opposite ends of the tankand dividing the tank into two superimposed compartments, said trackbeing adapted to receive bearings in abutting relation for bridging saidapertured track, a second tank surrounding the first tank and adapted toreceive electrolyte which leaks out of the first tank through saidapertures, pump means associated with the second tank and adapted topump electrolyte rom the second .tank into the first tank formaintaining the level of the electrolyte in the first tank at apredetermined level, and a feeding device adapted to feed bearingsprogressively to said track.

7. Apparatus for continuously electroplating semicylindrical bearings,comprising in combination; a first tank adapted to hold electrolyte andincluding apertures at opposite ends thereof, a longitudinally extendingapertured track connecting said apertures at opposite ends of said tankand dividing the tank into two superimposed compartments, said trackbeing adapted to receive bearings in abutting relation for bridging saidaperture, a second tank surrounding the first tank and adapted toreceive electrolyte which leaks out of the first tank through saidapertures, pump means associated with the second tank and adapted topump electrolyte from the second tank into the first tank formaintaining the level of the electrolyte in the first tank at apredetermined level, means for moving the track through said first tankcontinuously and a feeding device for progressively feeding hearings tothe track at one end thereof which bearings are progressively removedfrom the track at the other end thereof.

8. Apparatus for electroplating a plurality of semicylindrical bearingssimultaneously, comprising in combination; a tank adapted to holdelectrolyte and including a pair of opposed apertures in the end wallsthereof, a track passing through said tank and connecting said aperturesat opposite ends of said tank, said track being longitudinally slottedand of a dimension suflicient to substantially divide the tank into twosuperimposed compartments, means for holding anode metal in the lowercompartment, a cathode plate mounted in the upper compartment above saidtrack and extending substantially parallel thereto, a second tanksurrounding the first tank and adapted to receive electrolyte leaks outof said apertures and around said bearings, means associated with thefirst and second tanks for replenishing electrolyte in the first tankfrom electrolyte in the second tank, and means for progressively feedingbearings to said track at one end thereof whereby the bearings are movedalong the track through the electrolyte and between the electrodes andare electroplated during their passage through the tank.

9. The apparatus claimed in claim 8 including plug means within theapertures and dimensioned so as to be noninterfering with respect tosaid bearings, said plug means reducing the leakage of electrolytethrough said apertures.

10. The apparatus claimed in claim 8 wherein the track is an endlessconveyor belt which moves through said first and second tanks.

7. '11. The apparatus claimed in claim 8 wherein the track is a'stationary track and wherein the bearings are progressively movedtherealong by action of the feeding means.

References Cited in the file of this patent UNITEDSTATES PATENTS Thomaset a1 Sept. 27, 1955 "Martin et a1. May 8, 1956 Luecharler. Sept. '4,1956 Jackso Sept. 11, 1956 FOREIGN PATENTS Great Britain Sept. 16, 1948Great Aug. 21, 1946 Germany May 8, 1936

1. IN A METHOD FOR CONTINUOUSLY ELECTROPLATING THE CONCAVE SURFACES OF APLURALITY OF SEMICYLINDRICAL BEARINGS, THE STEPS COMPRISING, PROVIDING APLATING TANK CONTAINING AN ELECTROLYTE, PROVIDING A LONGITUDINALLYAPERTURED CONCEYOR TRACK WITHIN SAID TANK FOR LONGITUDINALLY DIVIDINGTHE TANK INTO TWO COMPARTMENTS, FEEDING SEMICYLINDRICAL BEARINGS TO SAIDTRACK SO THAT THE BEARINGS ABUT ONE ANOTHER AND BRIDGE THE APERTURE WITHTHEIR CONCAVE SURFACES FACING THE APERTURE AND ACT AS A BARRIER TOWARDFREE PASSAGE OF ELECTROLYTE FROM ONE COMPARTMENT TO ANOTHER THROUGH SAIDAPERTURE, POSITIONING AN ANODE IN THE LOWER COMPARTMENT OF SAID TANKBENEATH SAID TRACK AND IN SUBSTANTIALLY PARALLEL RELATION THERETO,POSITIONING A CONDUCTIVE PLATE IN THE UPPER COMPARTMENT ABOVE SAIDBEARINGS AND IN SUBSTANTIALLY PARALLEL RELATION TO SAID ANODE,ELECTRICALLY CONNECTING THE ANODE AND THE PLATE TO OPPOSITE POLES OF ACURENT SOURCE, PROGRESSIVELY MOVING THE BEARINGS ALONG SAID TRACK ANDBETWEEN THE ANODE AND THE PLATE WHILE MAINTAINING THE APERATURE BRIDGEDBY SAID BEARINGS, AND MAINTAINING THE ELECTROLYTE AT A LEVEL SUFFCIENTTO COVER SAID PLATE AT ALL TIMES.